Belt cleaner

ABSTRACT

A scraper for cleaning conveyor belts and the like includes an elongate blade holder with at least two support pins therein, and an elongate blade slidably received in a slot in the holder. The blade has an outer edge shaped for scraping a belt, and an inner edge abuttingly supported on the support pins at locations spaced a predetermined distance inwardly from the opposite ends of the blade. The blade is resiliently flexible along its length, such that as contact between the outer edge of the blade and the belt wears away the center portion of the blade, the end portions of the blade are flexed back about the support pins in the direction away from the belt, thereby bowing the center portion of the blade inwardly toward the belt for improved conformance and cleaning performance.

BACKGROUND OF THE INVENTION

The present invention relates to cleaners for conveyor belts and thelike, and in particular to a conforming scraper arrangement therefor.

Cleaners for conveyors are generally well-known in the art, and aretypically used to remove debris and other similar materials from variousforms of material conveying systems, such as conveyor belts, and thelike. Some types of belt cleaners employ a blade to scrape the debrisfrom the belt adjacent the upstream end of its return side, so as toimprove transport efficiency and to simplify debris collection andremoval. Examples of such scraper mechanisms are disclosed in U.S. Pat.Nos. 4,189,046; 4,402,394 and 4,936,439, which are hereby incorporatedherein by reference.

In many heavy duty commercial installations, such as at coal mines, rockquarries, etc., the debris from the conveyed material is quite abrasive,thereby causing the scraper blades to wear very quickly. Also, since amajority of the debris on heavy duty conveyor belts collects in thecenter portion of the belt, the scraper blades tend to wear unevenly,with the center portion of the scraper blade typically wearing much morerapidly than the end portions of the scraper blade. These factors oftenresult in poor cleaning performance, since scraper contact with the beltis non-uniform, and a significant maintenance problem is created,insofar as worn blades must be constantly replaced, sometimes under verydifficult circumstances, such as in underground mines.

SUMMARY OF THE INVENTION

One aspect of the present invention is to provide a scraper for cleaningconveyor belts and the like, which includes an elongate holder includingmutually parallel front and rear plates defining a groove therebetween,and at least two support pins extending between the front and rearplates at locations disposed a predetermined distance inwardly from theopposite ends of the holder. An elongate blade is mounted in the holder,and has opposite side faces closely received in the groove of the holderfor sliding movement therein, and opposite end portions positionedadjacent to the opposite ends of the holder. The blade has an outer edgeshaped for scraping a belt, an opposite inner edge abuttingly supportedon the support pins at locations thereon spaced a predetermined distanceinwardly from the opposite end portions of the blade, and a centerportion disposed generally centrally in the holder. The blade isresiliently flexible along its length, such that as contact between theouter edge of the blade and the belt wears away the center portion ofthe blade, the end portions of the blade are flexed back about thesupport pins in a direction away from the belt, thereby bowing thecenter portion of the blade inwardly toward the belt for improvedconformance and cleaning performance.

Preferably, the scraper includes a quick-change type of fastener systemto retain the blade in the holder, which permits the blade to be easilyremoved and replaced without tools. The quick-change fastener system isquite reliable, and is not adversely effected by even large build ups ofdebris and/or rust on the scraper, and is resistant to damage and/orjamming.

Another aspect of the present invention is to provide a scraper bladefor conveyor belt cleaners and the like of the type that includes aslotted blade holder with at least two support pins disposed inwardlyfrom opposite ends of the holder. The blade has opposite side facesshaped to be closely received in the holder for sliding movementtherein, as well as opposite end portions with outwardly extending tabsfor engaging fasteners to retain the blade in the holder. The blade hasan outer edge shaped for scraping a belt, and an opposite inner edgeshaped for abutting support on the support pins at locations spacedinwardly from the opposite end portions of the blade. The blade isresiliently flexible along its length, whereby as contact between theouter edge of the blade and the belt wears away the center portion ofthe blade, the end portions of the blade are flexed back about thesupport pins in a direction away from the belt, thereby bowing thecenter portion of the blade inwardly toward the belt for improvedconformance and cleaning performance.

The principal objects of the present invention are to provide aconforming belt cleaner which has improved cleaning performance andefficiency. The blade is resiliently flexible along its length, and bowsover holder support pins as the blade wears away to bow the centerportion of the blade inwardly to achieve better conformance with thebelt. A quick-change fastener system retains the blade in the holder,and is readily detachable to facilitate easy removal and replacement ofthe blade by even unskilled personnel without tools. The belt cleaner isalso very durable, and has an uncomplicated design, which renders itparticularly resistant to damage and/or jamming by debris, rocks, andthe like. The belt cleaner is efficient in use, economical tomanufacture, capable of a long operation life, and particularly welladapted for the proposed use.

These and other advantages will be further understood and appreciated bythose skilled in the art by reference to the following writtenspecification, claims and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of a scraper embodying the presentinvention, wherein a holder portion thereof has been broken away toreveal internal construction.

FIG. 2 is an exploded, side elevational view of the scraper, wherein ablade portion thereof and the holder are shown in a disassembledcondition.

FIG. 3 is an exploded, side elevational view of the scraper, wherein theblade is shown inserted into the holder, and a retainer pin is shown ina disassembled condition.

FIG. 4 is a vertical cross-sectional view of the scraper, shown in afully assembled condition, taken along the line IV--IV, FIG. 1.

FIG. 5 is a front elevational view of the scraper, shown in a worncondition abutting an associated conveyor belt, wherein a portion of theholder has been broken away to reveal internal construction.

FIG. 6 is a front elevational view of another embodiment of the presentinvention having a booster spring associated therewith, wherein a holderportion thereof has been broken away to reveal internal construction.

FIG. 7 is a side elevational view of a spring retainer associated withthe scraper illustrated in FIG. 6, shown in a preassembled condition.

FIG. 8 is a front elevational view of the spring retainer shown in FIG.7.

FIG. 9 is an enlarged, fragmentary vertical cross-sectional view of thescraper illustrated in FIG. 6, wherein the spring retainer is shownholding the booster spring in the holder.

FIG. 10 is a front elevational view of the scraper illustrated in FIG.6, shown in a worn condition abutting an associated conveyor belt,wherein a portion of the holder has been broken away to reveal internalconstruction.

FIG. 11 is a front elevational view of another embodiment of the presentinvention, having a blade and center mounted booster spring associatedtherewith, wherein a holder portion thereof has been broken away toreveal internal construction.

FIG. 12 is an end elevational view of the scraper illustrated in FIG.11, wherein a support pin portion thereof has been broken away to revealinternal construction.

FIG. 13 is a front elevational view of the scraper illustrated in FIG.11, shown in a worn condition abutting an associated conveyor belt,wherein a portion of the holder has been broken away to reveal internalconstruction.

FIG. 14 is a vertical cross-sectional view of the scraper illustrated inFIG. 11, taken along the line XIV--XIV, FIG. 13.

FIG. 15 is a vertical cross-sectional view of the scraper illustrated inFIG. 11, taken along the line XV--XV, FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of description herein, the terms "upper", "lower", "right","left" "rear", "front" "vertical", "horizontal", and derivatives thereofshall relate to the invention as oriented in FIG. 1. However, it is tobe understood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions and other physical characteristics relating to theembodiments disclosed herein are not to be considered as limiting,unless the claims expressly state otherwise.

The reference numeral 1 (FIG. 1) generally designates a scraperembodying the present invention. Scraper 1 is particularly adapted toclean conveyor mechanisms and the like, such as the illustrated conveyorbelt 2 (FIG. 5). Scraper 1 includes an elongate blade holder 3 with atleast two support pins 4 therein, and an elongate blade 5 slidablyreceived in a slot 6 in holder 3. Blade 5 has an outer edge 7 shaped forscraping conveyor belt 2, and an inner edge 8 abuttingly supported onsupport pins 4 at locations spaced a predetermined distance inwardlyfrom opposite end portions 9 of blade 5. The blade 5 is resilientlyflexible along its length, such that as contact between the outer edge 7of blade 5 and conveyor belt 2 wears away the center portion 10 of blade5, as shown in FIG. 5, the end portions 9 of blade 5 are flexed backabout support pins 4 in a direction away from the conveyor belt 2,thereby bowing the center portion 10 of belt 5 inwardly toward theconveyor belt 2 for improved conformance and cleaning performance.

With reference to FIGS. 1-5, the illustrated blade holder 3 includes afront plate 15 and a rear plate 16, which are interconnected in amutually parallel, spaced apart relationship, so as to form slot 6therebetween. Front plate 15 and rear plate 16 are similarly shaped,with a generally rectangular plan configuration, wherein each plateincludes an upper edge 17, a lower edge 18, and opposite end edges 19with inwardly tapered upper or outer portions 20. The lower edges 18 offront and rear plates 15 and 16 are generally aligned, and the width ofrear plate 16 is slightly greater than that of front plate 15, such thatthe upper edge 17 of rear plate 16 extends outwardly from the upper edge17 of front plate 15. Rear plate 16 is normally oriented toward thetrailing side of scraper 1, whereas front plate 15 is normally orientedtoward the leading side of scraper 1.

In the example shown in FIGS. 1-5, ten shouldered spacers 24 areprovided to fixedly interconnect front and rear plates 15 and 16 in aspaced apart relationship. Spacers 24 extend between holder plates 15and 16, and have opposite ends attached thereto by plug welding, or thelike. Five of the spacers 24 are positioned generally along the loweredges 18 of front and rear plates 15 and 16, and two of the spacers 24are positioned adjacent the upper edges 17 of front and rear plates 16adjacent end edges 20. Three of the spacers 24 are located adjacent thecentral portions of front and rear plates 15 and 16, and define backerpins, comprising two end support pins 4, and a single center support pin25, which function in the manner described in greater detailhereinafter. The backer support pins 4 and 25 are arranged in a colinearrelationship along holder slot 6, with each end support pin 4 beingdisposed a predetermined distance inwardly from the next adjacent end ofholder 4, so that the opposite ends of blade 5 are supported in acantilevered fashion. Preferably, the end support pins 4 are positionedin holder 4 such that the distance between each of the end support pins4 and the adjacent end portion of the blade 5 is equal to at least tenpercent of the overall width of blade 5, as measured along its outeredge 7, and a range of around 20-40 percent of the overall width ofblade 5 has been found to be satisfactory. In the illustrated example,the distance between end support pins 4 and the end edge 33 of blade 5is equal to around 25 percent of the overall width of blade 5.

A support pipe or tube 26 is fixedly attached to the exterior side ofrear plate 16 along the lower edge 18 thereof, and is adapted to mountscraper 1 to an associated scraper mechanism (not shown), such as themechanisms disclosed in previously referenced U.S. Pat. Nos. 4,189,046;4,402,394 and 4,936,439. Two pairs of aligned fastener apertures 27extend through front and rear plates 15 and 16, adjacent the oppositeinclined end edges 20, and are adapted to closely receive fastenerstherein to retain blade 5 in holder 3, as set forth below.

Scraper blade 5 (FIGS. 1-5) has an elongate shape with a generallyrectangular plan configuration, comprising outer edge 7 which is shapedfor scraping conveyor belt 2, inner edge 8 which is shaped for abuttingsupport on support pins 4 and 25, and opposite end edges 32, whichinclude inwardly tapered outer portions 33. The opposite end edges 32 ofblade 5 are shaped so as to form outwardly projecting tabs 34, whichfacilitate removably mounting blade 5 in holder 3 in the fashiondescribed below. Blade 5 is generally flat, and defines oppositelyoriented parallel planar faces 35 and 36. The inner edge 8 of theillustrated blade 5 is flat, and is disposed perpendicular to bladefaces 35 and 36, and the outer edge 7 of blade 5 is also flat, and formsa leading edge 37 at the front face 35 of blade 5. The outer edge 7 ofblade 5 may also be slightly angled in the nature of five to twentydegrees. The illustrated blade 5 is preferably constructed from asynthetic resin material, such as polyurethane, or the like, such thatit is quite durable, yet resiliently flexible along its length.

A pair of quick-release retainer pins 42 (FIGS. 1-5) are provided tosecurely retain blade 5 in holder 3 in a quick-disconnect fashion, so asto permit easy removal and replacement of blade 5 without tools by evenunskilled personnel. Retainer pins 42 include a ring 43 adjacent one endthereof to facilitate grasping the same, and a radially extendingaperture 44 through the opposite end thereof. Retainer pin 42 has agenerally cylindrical construction, and is shaped to be closely receivedwithin the aligned fastener apertures 27 in holder plates 15 and 16, asshown in FIGS. 3 and 4. When retainer pins 42 are fully inserted intothe aligned fastener apertures 27 in holder plates 15 and 16, theretainer pins 42 are positioned immediately adjacent the end tabs 34 onblade 5, thereby capturing blade 5 in holder 3 inbetween the tworetainer pins 42, and the three support pins 4 and 25. Each retainer pin42 includes a hair pin clip 45, which is received through the fasteneraperture 44 in retainer pin 42, so as to positively prevent pins 42 frombeing inadvertently removed from blade holder 5, yet permitting easyremoval of pins 42 for replacement of blade 5.

In operation, scraper 1 is assembled on an associated scraper mechanism(not shown), and adjusted so that the outer edge 7 of blade 5 comes intofull contact with the exterior or conveying surface of conveyor belt 2.When the blade 5 is new, as shown in FIG. 1, the inner edge 8 of blade 5is abuttingly supported on the two end support pins 4 and the centersupport pin 25. Blade 5 is free to flex about support pins 4 and 25 by asliding motion between holder plates 15 and 16. The center support pin25 provides positive support for blade 5 at the critical center portion10 thereof during the initial break-in of blade 5. Because of theabrasive nature of the debris being scraped from conveyor belt 2, theouter edge 7 of blade 5 is worn away during use. The debris on conveyorbelt 2 is typically concentrated near its center portion, such that thecenter portion 10 of blade 5 will normally wear away faster than the endportions 9 of blade 5, which is the condition illustrated in FIG. 5.

As the center portion 10 of blade 5 is worn away faster than the endportions 9 thereof, the resilient flexibility of blade 5 is such thatthe end portions 9 of blade 5 are flexed back into the holder 5. Thisflexing motion takes place about the end support pins 4, and is in adirection away from the conveyor belt 2, thereby arching or bowing thecenter portion 10 of blade 5 inwardly toward the conveyor belt 2,thereby providing better conformance with the conveyor belt 2, andimproved cleaning performance. This bowing action lifts the centerportion 10 of blade inner edge 8 off of the center support pin 25, asshown in FIG. 5. The outer end portions 9 of blade 5 are in factsupported in a cantilevered fashion from end support pins 4, such thatthe force applied to blade end portions 9 by the conveyor belt 2elastically deforms blade 5 to assume an arcuate plan shape. This bowingor flexing action makes the blade 5 self-adjusting or self-regulating,so as to achieve maximum blade conformance at the critical center areaof the conveyor belt 2. The contact force between the opposite endportions 9 of blade 5 and the conveyor belt 2 is, through the bowingcantilever flexing of blade 4, redirected to force the center portion 10of blade 4 into the conveyor belt 2. Hence, even though blade 4 wearsmost quickly at its center portion 10, good blade conformance ismaintained at the center area of the conveyor belt 2. In the worncondition illustrated in FIG. 5, when the scraper 1 is moved away fromconveyor belt 4, the inner edge 8 of blade 5 assumes its normal linearcondition, supported on each of the support pins 4 and 25, and the outeredge 7 of blade 5 assumes a generally concave shape.

A worn blade 5 can be easily removed from blade holder 3 and replaced,without the need for tools or highly skilled repair personnel. Toreplace a worn blade 5, the operator simply removes the clip 45 from atleast one of the two retainer pins 42, and then withdraws the retainerpin 42 from the plates 15 and 16 of holder 3. Blade 5 can then be easilyremoved from holder 3 by sliding it outwardly of holder slot 6, out fromunder the remaining retainer pin 42. Alternatively, both retainer pins42 can simply be removed from both ends of holder 3. A new blade 5 isthen similarly inserted into holder slot 6. Each removed retainer pin 42is then reinserted in aligned fastener apertures 27, and an associatedclip 45 is mounted in place to positively retain scraper 1 in its fullyassembled condition. Blade 5 can be easily removed and replaced evenwhen there are large deposits of debris or rust on scraper 1, and/or indifficult environments, such as in underground mines.

The reference numeral 1a (FIGS. 6-10) generally designates anotherscraper embodying the present invention, having a booster spring 50associated therewith. Since scraper 1a is similar to the previouslydescribed scraper 1, similar parts appearing in FIGS. 1-5 and FIGS. 6-10respectively are represented by the same, corresponding referencenumeral, except for the suffix "a" in the numerals of the latter. Inscraper 1a, booster spring 50 is mounted in holder 3a by a pair ofS-shaped spring retainers 51. The illustrated booster spring 50 is inthe nature of a leaf spring, and has a width substantially commensuratewith the width of blade 5, and a length slightly longer than the inneredge 8 of blade 5. Booster spring 50 may be constructed from a springsteel, or other similar material, and is designed to provide additionalspring force or flex resistance to blade 5, particularly when scraper 1is used in conjunction with very wide conveyor belts 2, therebyrequiring a long scraper blade 5.

Spring retainers 51 have a substantially identical construction, and arepositioned adjacent the opposite ends of blade holder 3a. The springretainer 51 illustrated in FIGS. 7 and 8 is shown in a pre-assemblycondition, and includes a hook-shaped upper end 55, a crimped centerportion 56 that forms an inwardly protruding ledge, and a straight lowerend 57, which is formed into a hook during assembly, as shown in FIG. 9.Scraper 1a is assembled in the following fashion. Booster spring 50 isinserted into the slot 6a in blade holder 3a, and is abuttinglysupported on support pins 4a and 25a. Two spring retainers 51 arepositioned adjacent the opposite ends of booster spring 50, with theirupper ends 55 engaged over the outermost spacers 24a, and their centerledges 56 positioned over the outward end surfaces of booster spring 50in the manner illustrated in FIG. 9. The lower ends 57 of springretainers 51 are then bent back into a hook around the outermost spacers24a, so as to securely, yet slidably mount booster spring 50 in slot 6a,between the front and rear plates 15a and 16a of blade holder 3a. Ablade 5a is then inserted into blade holder 3a, so that its inner edge8a rests on the outwardly facing surface of booster spring 50.Quick-release retainer pins 42a and clips 45a are then installed inblade holder 3a in the manner similar to that described hereinabove.

During operation, scraper 1 a performs in a manner similar to thepreviously described scraper 1. As shown in FIG. 10, as the centerportion of 10a of blade 5a is worn away, the opposite end portions 9a ofblade 5a, as well as the opposite end portions of booster spring 50, areflexed back about the end support pins 4a in a direction away from theconveyor belt 2a, thereby arching or bowing the center portion 10a ofblade 5a and the center portion of booster spring 50 inwardly toward theconveyor belt 2a for improved conformance and cleaning performance. Inthe worn condition illustrated in FIG. 10, the center portion of boosterspring 50 lifts off of the center support pin 25a. Booster spring 50imparts additional stiffness or spring force to blade 5a, particularlyin very wide scrapers 1a, to insure proper conformance with theconveying surface of the conveyor belt 2a.

The reference numeral 1b (FIGS. 11-15) generally designates anotherscraper embodying the present invention, having a scraper blade andcenter mounted booster spring. Since scraper 1b is similar to thepreviously described scrapers 1 and 1a, similar parts appearing in FIGS.1-5 and FIGS. 6-10, and FIGS. 11-15 respectively are represented by thesame, corresponding reference numeral, except for the suffix "b" in thenumerals of the latter. A U-shaped spring retainer 62 is mounted to thecenter portion of booster spring 50b by fasteners 63. The center supportpin 25b is slidingly received within the interior of U-shaped springretainer 62. In this fashion, spring retainer 62 positively locatesbooster spring 50b longitudinally within holder 3b, yet permits thecenter portion of booster spring 50b, as well as the center portion of10b of blade 5b to float inwardly and outwardly in holder slot 6b, asshown in FIG. 13.

The assembly of scraper 1b (FIGS. 11-15) is similar to that describedabove with respect to scraper 1, except that booster spring 50b is firstpositioned in holder slot 6b, and the U-shaped spring retainer 62 ispositioned over the center support pin 25b, and attached to boosterspring 50b by fasteners 63.

During operation, scraper 1b performs similarly to the previouslydescribed scrapers 1 and 1a. As contact between the outer edge of 7b ofblade 5b and the conveyor belt 2b wears away the center portion 10b ofblade 5b, the outer end portions 9b of blade 5b, as well as the oppositeend portions of booster spring 50b, are flexed back about the endsupport pins 4b in a direction away from the conveyor belt 2b, therebyarching or bowing the center portion 10b of the blade 5b and the centerportion of booster spring 50b inwardly toward the conveyor belt forimproved conformance and cleaning performance.

Scrapers 1-1b provide a unique conforming belt cleaner, which hasimproved cleaning performance and efficiency. The longitudinalresiliency of the blades 5-5b, and their sliding mount within holders3-3b permit the blades 5-5b to arch or bow over holder support pins 4-4bas the blade wears to achieve better conformance with the belt.Quick-change retainer pins 42-42b securely retain the blades 5-5b intheir associated holders 3-3b, and are readily detachable to facilitateeasy removal and replacement of the same without tools by even unskilledpersonnel.

In the foregoing description, it will be readily appreciated by thoseskilled in the art that modifications may be made to the inventionwithout departing from the concepts disclosed herein. Such modificationsare to be considered as included in the following claims, unless theseclaims by their language expressly state otherwise.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A scraper for cleaningconveyor belts and the like, comprising:an elongate holder includingmutually parallel front and rear plates defining a groove therebetween,and at least two support pins extending between said front and rearplates at locations disposed a predetermined distance inwardly fromopposite ends of said holder; an elongate blade mounted in said holder,having opposite side faces closely received in the groove of said holderfor sliding movement therein, and opposite end portions positionedadjacent to the opposite ends of said holder; said blade having an outeredge shaped for scraping a belt, an opposite inner edge abuttinglysupported on said support pins at locations thereon spaced apredetermined distance inwardly from the end portions of said blade, anda center portion disposed generally centrally in said holder; said bladebeing resiliently flexible along its length, whereby as contact betweenthe outer edge of said blade and the belt wears away the center portionof said blade, the end portions of said blade are flexed back about saidsupport pins in a direction away from the belt, thereby bowing thecenter portion of said blade inwardly toward the belt for improvedconformance and cleaning performance.
 2. A scraper as set forth in claim1, including:a quick-change fastener retaining said blade in saidholder, and being easily detachable to facilitate replacement of saidblade.
 3. A scraper as set forth in claim 2, wherein:said blade has anoverall width measured between the opposite end portions of said blade;and said support pins are positioned in said holder such that thepredetermined distance between each of said support pins and theadjacent end portion of said blade is equal to at least ten percent ofthe overall width of said blade.
 4. A scraper as set forth in claim 3,wherein:said fastener includes a pair of quick-release retainer pinsextending between said front and rear plates and capturing said blade insaid holder.
 5. A scraper as set forth in claim 4, wherein:said bladeincludes opposite end edges with outwardly extending tab portions whichengage said retainer pins to removably mount said blade in said holder.6. A scraper as set forth in claim 5, including:a third support pinextending between said front and rear plates at a location generallyintermediate and colinear with said two support pins.
 7. A scraper asset forth in claim 6, including:a booster spring positioned along theinner edge of said blade and providing additional spring force to saidblade.
 8. A scraper as set forth in claim 7, including:a plurality ofspacers extending between said from and rear plates, and fixedlyinterconnecting the same in a spaced apart relationship.
 9. A scraper asset forth in claim 8, including:a U-shaped spring retainer connectedwith said booster spring and slidingly receiving said third support pintherein.
 10. A scraper as set forth in claim 8, including:a pair ofS-shaped spring retainers extending between adjacent spacers andincluding an inwardly projecting ledge which engages opposite ends ofsaid booster spring to retain the same in said holder.
 11. A scraper asset forth in claim 10, wherein:said support pins are positioned in saidholder such that the predetermined distance between each of said supportpins and the adjacent end portion of said blade is in the range oftwenty to forty percent of the overall width of said blade.
 12. Ascraper as set forth in claim 11, wherein:said support pins arepositioned in said holder such that the predetermined distance betweeneach of said support pins and the adjacent end portion of said blade isequal to around twenty five percent of the overall width of said blade.13. A scraper as set forth in claim 1, wherein:said blade has an overallwidth measured between the opposite end portions of said blade; and saidsupport pins are positioned in said holder such that the predetermineddistance between each of said support pins and the adjacent end portionof said blade is equal to at least ten percent of the overall width ofsaid blade.
 14. A scraper as set forth in claim 1, including:a pair ofquick-release retainer pins extending between said front and rear platesand capturing said blade in said holder.
 15. A scraper as set forth inclaim 1, wherein:said blade includes opposite end edges with outwardlyextending tab portions to removably mount said blade in said holder. 16.A scraper as set forth in claim 1, including:a third support pinextending between said front and rear plates at a location generallyintermediate and colinear with said two support pins.
 17. A scraper asset forth in claim 1, including:a booster spring positioned along theinner edge of said blade and providing additional spring force to saidblade.
 18. A scraper as set forth in claim 17, including:a U-shapedspring retainer connected with said booster spring.
 19. A scraper as setforth in claim 17, including:a pair of S-shaped spring retainersincluding inwardly projecting ledges which engage opposite ends of saidbooster spring to retain the same in said holder.
 20. A scraper as setforth in claim 1, including:a plurality of spacers extending betweensaid front and rear plates, and fixedly interconnecting the same in aspaced apart relationship.
 21. A scraper as set forth in claim 1,wherein:said blade has an overall width measured between the oppositeend portions of said blade; and said support pins are positioned in saidholder such that the predetermined distance between each of said supportpins and the adjacent end portion of said blade is in the range oftwenty to forty percent of the overall width of said blade.
 22. Ascraper as set forth in claim 1, wherein:said blade has an overall widthmeasured between the opposite end portions of said blade; and saidsupport pins are positioned in said holder such that the predetermineddistance between each of said support pins and the adjacent end of saidblade is equal to around twenty five percent of the overall width ofsaid blade.
 23. A scraper blade for conveyor belt cleaners and the likeof the type that include a slotted blade holder with at least twosupport pins disposed inwardly from opposite ends of the holder; saidblade comprising:opposite side faces shaped to be closely received inthe holder for sliding movement therein; opposite end portions withoutwardly extending tabs for engaging fasteners to retain said blade inthe holder; an outer edge shaped for scraping a belt, and an oppositeinner edge shaped for abutting support on the support pins at locationsspaced inwardly from the opposite ends of said blade; a center portiondisposed generally centrally in said holder; and wherein said blade isresiliently flexible along its length, whereby as contact between theouter edge of said blade and the belt wears away the center portion ofsaid blade, the end portions of said blade are flexed back about thesupport pins in a direction away from the belt, thereby bowing thecenter portion of said blade inwardly toward the belt for improvedconformance and cleaning performance.
 24. A scraper blade as set forthin claim 23, including:a booster spring positioned along the inner edgeof said blade and providing additional spring force to said blade.